Propellent powder



: Patented Nov. 4, 1941 PROPELLENT POWDER Walter P. Regestein,Wilmington, Del., assignor to E. I. du Pont de Nemours & Company,Wilmington, DeL, a corporation of Delaware No Drawing.

Application December '1, 1938,

Serial No. 244,347

6 Claims.

My invention relates to an improvedpropellent powder and in particularto an improved nitrocellulose powder of the cellular type.

It is well known that an important ballistic problem confronting thesmokeless powder manufacture is that of producing powders which at- Itain a given velocity with the employment of a weight of chargesufliciently low to provide operable pressures.

Heretofore propellent powders of the cellular type have beencommercially unsatisfactory in the above respects. By cellular powders Imean those containing cells wherein the solid has been displaced withinthe body of .the grain to form minute pockets therein. Such powders aremade conventionally by including soluble solids within the structure ofthe colloid and later dissolving out said solids therefrom to.leave thehollow cells therein.

Such powders of the prior art have been commercially unsatisfactory inthat they have been characterized by lack of complete combustionresulting in unusually high residue, exceptionally high weights-ofcharge for a given velocity, and pressures so high as to beunsatisfactory. This is particularly true of the so-called densenitrocellulose powders of the cellular type as prepared according to theprior art. The term dense nitrocellulose powder has taken on a fixedmeaning in the art and commonly refers to a nitrocellulose powder inwhich the colloid has been compressed in the process of manufacture,such as by means of a press through dies into ribbons, cords, tubes orthe like, or by' means of rolls into sheets, and in general withsubsequent subdivision by means of a cutting machineinto grains ofsuitable size. Naturally, loading companies have avoided the use ofcellular powder of this type, due to the aforesaid high weight of chargerequired for a given velocity and to avoid complaints from excessivepressures, high residue after burning, and the like.

An object of my present invention is a cellular powder of improvedballistic properties. A further object is such a powder characterized byhighly efficient burning properties as measured by extremely lowresidue. Another object is a dense nitrocellulose powder of the cellulartype characterized by low weights of charge, low residues and lowpressuresat given velocities. A

cellulose, and subsequently removing therefrom, a soluble solid materialsuch as sugar, for ex- 8X Powdered 4X Powdered further object is aprocess for producing said improved cellular powder.

I have found that the foregoing objects are accomplished and thedisadvantages overcome by intimately incorporating in the colloidednitro- The most important application of my invention is in theso-called dense nitrocellulose powders." For the purpose of the presentspecification and claims, the term "dense nitrocellulose powders shallbe taken to refer to that powder in which the colloided nitrocelluloseis processed by the application of a compressing force. This powder isusually extruded through dies by means of applying pressure to a colloidcontained in a press, or is compressed into thin sheets by passingthrough rolls. Th dense nitrocellulose powder is thus to bedistinguished from the so-called voluminous or bulk nitrocellulosepowder which undergoes no such compressing step.

The following is a typical method for the manufacture of a densenitrocellulose powder according to my invention.

The powder is preferably made from two nitrocelluloses of differentnitrogen contents, one soluble in a mixture of two parts of ether to oneof ethyl alcohol, and the other of high nitrogen content, practicallyinsoluble in the same solvent mixture. These two nitrocelluloses arethoroughly blended in the pulped condition by stirring under water. Theblend may have 1;; nitrogen content varying from 12.90 to 13.30% with asolubility in ether-alcohol from about 50 to 20%, depending on theamount of each type of nitrocellulose used in making up the blend, whichin turn is dependent on the particular purpose for which the powder isto be used. The wet blend of nitrocellulose is wrung in a centrifugalwringer to leave about 30% of water in it. The water wet nitrocelluloseis then dehydrated in a dehydrating press by means of ethyl alcohol. Theblocks of dehydrated nitrocellulose containing the desired amount ofalcohol are broken up and placed in a mixing machine. The ether is thenadded so that the ratio of ether to alcohol is approximately two partsof the former to one of the latter, and the total quantity of ,solventpresent is approximately equal to the dry weight of the nitrocellulose.The pulverized sugar is added at this point. Diphenylamine is usuallyadded as a stabilizing agent together with any other special ingredient.The mass of these various ingredients is mixed for about one hour,during which process the ether-alcohol solvent mixture colloids only thesoluble nitrocellulose present in the blend, the insolublenitrocellulose remaining suspended in the colloid in an ungelatinizedcondition. The sugar, of course, is intimately distributed within thebody of the colloid. The colloid,

after mixing, .is formed into blocks by means of a suitable press andthese blocks transferred 'to a powder press there, by the use ofconsiderable pressure, the colloid is forced through dies into cords,tubes or ribbons, which are then cut into small grains by means of acutting machine. These powder grains may be subjected to a solventrecovery treatment to recover the ether and alcohol, and/or a watertreatment in which the powder grains are steeped in hot water to leachout the sugar therefrom, leaving a powder having the improved finecellular texture according to .the present invention. The powder grainsmay be dried at this point, then glazed and sieved and used as anon-coated powder for a great variety of purposes in rifles, shotguns,pistols and revolvers, in fact in all kinds of small arms.

However, where increased velocity is desired the powder grains aresubjected to a surface moderating treatment with dinitrotoluol,dimethyldiphenylurea, or other suitable surface moderating agents, byone of the several wellknown methods, and then finally dried, glazed andsieved. These surface coated powders are also used in all kinds of smallarms, the fundamental principle of their use in shot shells being thesame as in their use in rifle cartridges.

In order to further illustrate my invention in greater detail, I havesummarized in the table given below the results of ballistic testsobtained on three samples of powder in the .22 caliber long rifle, usinga high velocity cartridge case with a 40-grain lead bullet. Thesepowders were all made from a blend of nitrocellulose having a nitrogencontent of 13.20% with a solubility in ether-alcohol mixture of about30%. All powders contain 0.6% of diphenylamine calculated on the dryweight of nitrocellulose used. The samples were made up with parts ofsugar added at the mixer per 100 parts of nitrocellulose (dry weight)Sample 1 with 4X pulverized sugar, and Sample 2 with granulated sugar asemployed in the art. After thorough mixing and colloiding, the threecompositions were pressed through dies having diameters of .041 of aninch and cut into grains having a length of A of an inch. The powdersfrom the cutting machine were immediately placed in hot water at atemperature of 55 C. in order to removethe solvent and leach out thesugar. These powders were treated several days in hot water to completethe leaching process. The powders were then removed and surfacemoderated with dimethyldiphenylurea. These surface moderated powderswere then dried, glazed and sieved. The ballistic results were asfollows:

Table II t: w m I t M 31 me e erg ns can no Sample g ggi density ofvelocity presfrom of charge 25 sure 100 powder rounds ioot- LbsJ PerGrains aecemda sq. in. cent 4X pulverized 630 2. l, 298 23, 080 5. 32Granulatei. 647 2. 60 1, 303 26, 760 10. None 694 2. 70 1, 305 24, 23010. 45

The pressures given in the above table were recorded with copper crushercylinders having a diameter of .179 inch and a length of .400 inch, in apressure gauge having a piston hole located at the mouth of thecartridge case. Lower pressures are recorded by the use of lead crushercylinders or by making the pressure tests under other conditions."

Sieve tests on the granulated sugar employed in the abovecomparisonshowed 56.8% coarser than 35-mesh (.0164 inch), 38% between 35 and65-mesh (.0164 inch-.0082 inch), and substantially all the rest between65 and -mesh (.0082 inch-.0058 inch).

Comparing the results between Sample 1, 'according to my invention, andSample 2, made with sugar of the size employed in the prior art, it willbe noted that Sample 1, made with the pulverized sugar, burns so muchmore efliciently than Sample 2, made with the sugar of the size employedin the art, that the residue of the former is less than that of thelatter, while a weight of charge of only 2.2 grains is required for theformer to produce a given velocity as compared with 2.6 grains for thepowder of the art. Furthermore, it will be noted that a much lower, andaccordingly much more satisfactory; pressure is obtained with the powderof my invention. The residue is calculated on the basis of 100 roundsfired in the .22 caliber long rifle. This residue represents, chiefly,unburned powder collected from a very large sheet of paper placed infront of the rifle, plus any residue remaining in the gun after firingthe 100 rounds. Furthermore, the amount of residue from 100 rounds ofSample 1 was less than the residue from 100 rounds loaded with a surfacemoderated nitrogylcerin powder fired for comparison. Sample 3 indicatesthe disadvantages of a non-cellular dense nitrocellulose powder.

I attribute the improvement in ballistic qualities and burningcharacteristics of Sample 1 over Sample 2 to the presence of an almostinfinite number of microscopic cells distributed throughout the powdergrains in Sample 1 as contrasted with the relatively large pores presentin Sample 2, made with granulated sugar according to the art.

In addition to determining the marked improvement in ballistic qualitiesobtained with the use of the pulverized sugar, I have also determinedthat by varying the fineness of subdivision of 'the pulverized sugaremployed, and by varying the amounts of said sugar employed, I mayproduce powders adequate for a largevariety of cartridges for use in allkinds of small arms where any given velocity is desired with a minimumof pressure and a minimum of unburned powder. The following table showsthe ballistics obtained on various samples of uncoated powders in whichthe pulverized size has been varied over a considerable range. Thepowders were tested under the same conditions as the samples of -meshscreen.

Table II, previously mentioned, but at a lower velocity as indicated.

.22 caliber long rifle components, the bullet weighing 40 grains.Pressures were recordedwith Winchester 146L400 coppers. Each test repre-In general, the effect of increasing the fineness of the pulverizedsurgar employed appears I to be a lowering in the weight of the chargewhile maintaining the ballistics fairly constant, This effect is mostnoticeable in the coated powders which are shot at higher velocity. Thesmall differences in pressure can be accounted for by the non-uniformityin components. In Table V a similar situation is shown with respect toboth coated and uncoated powders with various types of sugar obtained byblending standard grades so that the given "percentage through-200-meshis known.

Table V Sam S Weight 5523 Mean Coat- I ple g of charge Over 50 pressureing Liza/sq. l1 Grains in. Parts l 50% thru 20041113511- 1. 61 l, 15422, 370 None ll 75% thru mil-mesh. l. 60 l, 154 20, 370 None I 12 6Xsugar l. 56 1, 151 None 13 50% thru ZOO-mesh. 2. 2| 1, 300, 26, 150 3l4. 75% thru 200-mesh. 2. 18 1, 303 24, 000 3 15.- 6X sugar 2. 12 1, 29925, 590 3 16".. 50%thru 200-mesh... 2.28 1,300 23,630 3% 17.. 75% thrumil-mesh 2. 23 l, 299 22, 820 3% 18. 6X sugar 2. 18 1, 300 21, 800 3%Coating was .dimethyldiphenylurea.

In the preparation of the above samples, the composition of the powderwas 100 parts of nitrocellulose, parts of sugar, and "0.6%diphenylamine. The various mixtures of sugar employed were obtained byblending standard 6X sugar with a, slightly coarser sugar in suchproportions that 50 or 75% of the sugar would pass a 200- The powderwasgranulated at .041 x 1/150. Tests of both coated and uncoated I powderwerermade in theRemington Hi-Speed Table III sents a 10 shot series, Theuncoated powders G 5 show a slight. but distinct lowering of "the weightravi- Sam s meme Weight Inst: Mean of charge as the size of the sugarparticles deple 128 of sugar used delzsflty chgige prw creases. In thecase of the coated powders thispowder Sure effect is more pronounced.Further variations in properties of the powders v 10 were obtained byvarying the percentage of sugar. /115 mesh 567 f g incorporated therein,as shown in the following mesh 570 1.52 1,152 221470 table: 7 e Thrumesh 550 1.51 1,151 22,460 Table The sugar size is given in terms of themesh 15 43mg 7 through which all of the material passes along Samplesugar metric Weight X. Mean with the mesh on which all is held. Forinstance, oi fit tii er wilds mm 100/115 indicates that substantiallyall passed through a 100-mesh and substantially all is held Per may, ona 115- mesh, It will be noted from the fore- 20 cm! Grains 4 going tablethat the weight of charge can be $3 3 lowered appreciably by varying thetype of pul- 15 1:160 verized sugar employed. The same situation is 2{:22 i1 f8 313 shown in Table IV with respect to powders coated I 485 391-158 291870 with three parts of dimethyldiphenylurea. 58 $33 113,8 ,1;it? 25123 Table IV These results show an increase in emciency' as theSam (ivy I ht Inst M perezergage of sugar ifs inerl easedhsnce tehefp311- size orsu mused me 1'10 '91 v loci't can VB! e sugar 1S pre era y83.0 e 011 0 e P g f gg fig charge 2513 pressure 30 powder by steepingwith hot water, it is customary to refer to the amount used as so many GFew flirts based on 101? parts of nitrocellulose rather ra ns sec s in.an on a percen age basis of composition. Be- Zjiji: "iiiiiifi 233211: 1.32 3:53 1:333 it?" tween 5 and 25% of sugar, the ballistics are Thru180 mesh-U. 5 -06 1,304 7,7 35 practically the same, while the weight ofcharge drops progressively from 1.75 grains to 1.44

powders satisfactory with respect to pressures, I

with very low weights of charge, adequate velocity, and extremely lowresidues. It will be appreciated that the size of the cells .in thefinished powder will be measured by the size of the sugar displacedtherefrom, with allowance for small changes which the powder goesthrough in the leaching and drying stages.

In particular, the powders of my invention are characterized byrelatively high gravimetric densities. It is true, for example, that inspite of the cellular structure obtained, my dense nitrocellulosepowders have gravimetric densities much higher than the so-calledvo1uminous" or bulk powders. My powders are particularly useful in alarge variety of cartridges for usein all kinds of small arms where thehighest velocity is desired with a minimum of pressure and a minimum ofiinburned powder.

I do not limit myself to any particular amount of moderating agent usedin the manufacture of my powder. I have found that the amount ofdimethyldiphenylurea, for example, can be in- I creased or decreased inaccordance with the purpose for which the powder is intended. In placeFurthermore, I do not limit myself to the values of nitrogen content orsolubility of the nitrocellulose given above, it being understood thatthe compositions given are for the purpose of illustration only. WhileI. prefer to use a mixture of two types of nitrocellulose, one solublein and the other insoluble in an ether-alcohol mixture, it should beunderstood that my invention relates to improvements in densenitrocellulose powders whether they be made from one type ofnitrocellulose obtained in a single nitration or a blend of two or moretypes of nitrocellulose obtained in two separate nitrations underdifi'erent nitrating cqnd My invention is also applicable to densenitrocellulose powders in which the colloid containing the pulverizedsugar may be, after drying, subdivided by grinding and sieving insteadof being subdivided while soft by means of cutting machines:Furthermore, my invention is not limited in principle to the densenitrocellulos powder but is applicable generally to nitrocellulosepowders as a whole. Indeed, it may be applied to powders containingnitroglycerine as well as nitrocellulose. However, it should beremembered that by far the most beneficial effects are obtained whenapplying the same to the dense nitrocellulose powder.

Although I have described my invention in the foregoing with particularreference to the use of sugar as the soluble solid material which isdisplaced from the powder, it should be clearly understood that this ismerely the preferred form of the invention, and that the invention isnot limited to sugar alone but includes soluble solids in general, suchas, for example, soluble salts of the type of potassium nitrate or thelike.

I particularly do not limit the use of powders made in accordance withmy invention to rifle cartridges. I have found that the powders are verysuitable for use in all types of small arms, shotguns, pistols andrevolvers, in addition to sporting and military rifles. For example, thefollowing table demonstrates the suitability of my improved cellularpowder for use as a shotgun load.

Both of these powders give ballistic results which compare favorablywith standardiconventional shotgun powders, but have the additionaladvantage of being much cleaner burning.

Accordingly, I intend to be limited only in accordance with thefollowing patent claims:

I claim:

l. The process of producing a dense nitrocellulose powder of improvedburning characteristics which comprises forming the colloid,incorporating in the colloid pulverized sugar of such a state ofsubdivision that substantially all the particles thereof pass through astandard loo-mesh screen having openings of .0058 of an inch in width,subjecting said colloid to a compressing force, forming said compressedcolloid into grains, and leaching out said sugar from said grains.

2. The process of producing a dense nitrocellulose powder of improvedburning characteristics which comprises forming the colloid,incorporating in the colloid pulverized sugar of such a state ofsubdivision that the greater part thereof passes through a ZOO-meshscreen having openings of .0029 of an inch in width, subjecting saidcolloid to a compressing .force, forming said compressed colloid intograins, and leaching out said sugar from said grains.

3. The process of producing a dense nitrocellulose powder.of improvedburning characteristics which comprises forming the colloid,incorporating in the colloid from 5 to 25% of pulverized sugar based onthe weight of nitrocellulose, said sugar being in a state of subdivisionsuch that substantially all the particles thereof pass through astandard IOU-mesh screen having openings of .0058 of an inch in width,subjecting said colloid to a compressing force, forming said pressedcolloid into grains, and leaching out said sugar from said grains beforedrying them.

4. A dense nitrocellulose powder of improved burning characteristicscomprising colloided ni- 5. A dense nitrocellulose powder ofimprovedburning characteristics comprising colloided nitrocellulosehaving a fine cellular texture resulting from the removal therefrom ofpulverized sugar of such a state of subdivision that the greater partthereof passes through a 200-mesh screen having openings of .0029 of aninch in

